The compound dimethyl 2-formyl-2-methylglutarate is an important intermediate for producing amines or diols or triols. Whether the former or latter is produced depends whether the intermediate dimethyl 2-formyl-2-methylglutarate is subsequently subjected to reductive amination or reduction, respectively. The diesters, amines and diols or triols are important in polymer applications, such as polyesters. However, nothing in the prior art teaches or suggests a convenient method for synthesizing these intermediate compounds. Nowhere is there described a catalyst system such as in the instant process for producing these intermediates from acrylates and synthesis gas by a novel reaction.
Murata et al. have reported on the relative activity of various complexes formed in situ from dicobalt octacarbonyl and various di(tertiary phosphines) as ligands for the hydroformylation of methyl acrylate. The complexes are more active than Co.sub.2 (CO).sub.8 alone and the most active of the catalyst complexes was active even at low pressures where decomposition of Co.sub.2 (CO).sub.8 occurs. See Bull. Chem. Soc. Jpn. 53, 214-218 (1980).
A study reported by Jardine in Polyhedron, No. 7-8, 569-605, 1982 provides further insight into a comparison of carbonylhydrido tris(triphenylphosphine)rhodium(I) RhH(CO)(PPh.sub.3).sub.3 as a hydroformylation catalyst and concludes that though RhH(CO)(PPh.sub.3).sub.3 is the best hydroformylation catalyst, that it is disappointing in other reactions, that chlorotris(triphenylphosphine)rhodium(I) is probably a more generally useful hydrogenation catalyst and dichloro tris(triphenylphosphine)ruthenium(II) is probably a more effective isotope exchange catalyst.
In J. Mol. Cat. 16 (1982) 195-207, Mitsuo et al. describe experiments wherein phosphine complexes are used in conjunction with rhodium-catalyzed low pressure hydroformylation of typical terminal olefins at pressures substantially lower than will normally work.
In J. Falbe, "New Syntheses With Carbon Monoxide", Springer-Verlag, Berlin Heidelberg New York 1980, Chapter 1 discusses the hydroformylation of methyl acrylate by using rhodium and cobalt catalysts (page 119 and 120). Under similar reaction conditions, a cobalt catalyst is used to hydroformylate methyl acrylate to produce methyl .beta.-formylpropionate as the predominant product. In contrast, rhodium produced .alpha.-formylpropionate as the major product. Furthermore, the selectivity was affected by the addition of triphenylphosphine.
Generally in the prior art what is taught or suggested is the rhodium catalyzed hydroformylation of, for example, olefins. Nothing in the art teaches the novel reaction of the instant invention wherein diesters are formed via the hydroformylation/Michael addition of alkyl acrylates. This appears to be a new reaction. It would be desirable to invent a process for such a reaction, especially if the conversion and selectivity for the desired diesters were high. These diesters can be used as intermediates for producing amines, diols and triols.